The present invention relates to apparatus for trimming paper sheets or the like, and more particularly to improvements in apparatus for trimming the lateral marginal portions of sheets which are transported seriatim along a predetermined path. Still more particularly, the invention relates to improvements in trimming apparatus of the type wherein the marginal portions of sheets or accumulations of sheets are trimmed by cooperating counterknives and orbiting knives adjacent to one or more portions of a path which is defined by the means for transporting the sheets.
Apparatus for trimming marginal portions of paper sheets or the like are disclosed in German Offenlegungsschrift No. 25 58 045 and in U.S. Pat. No. 3,813,981 granted Jun. 4, 1974 to Faltin. The German publication discloses an apparatus including a rotary disc-shaped knife having a circular cutting edge and cooperating with the circular cutting edge of a rotary counterknife. Such apparatus is capable of adequately trimming relatively thin sheets or relatively thin piles of overlapping or folded sheets. It has been found, however, that the apparatus which is described in this German publication is not suited for trimming relatively thick newspapers, brochures, pamphlets or analogous accumulations of superimposed or folded-over sheets. Even relatively thin sheets or relatively thin accumulations of sheets are likely to slide relative to the circular cutting edges of the knife and counterknife.
The apparatus of U.S. Pat. No. 3,813,981 to Faltin is more suitable for the trimming of marginal portions of relatively thick accumulations of sheets, such as newspapers, brochures or the like. However, this apparatus exhibits the drawback that the trimming operation is satisfactory only if the peripheral speed of the rotary knives matches the speed at which the material to be trimmed is advanced past the cutting station. Furthermore, the trimming action is adversely affected by the recessed cutting edges, and the dimensions of trimmed sheets merely approximate but cannot exactly match the optimum dimensions.